1. Field of the Invention
This invention relates to tube cutoff apparatuses and in particular to such apparatuses utilizing blade cutoff means.
2. Description of the Prior Art
As shown in U.S. Pat. No. 683,289 of Hugo John, girders, angle irons, and the like, may be cut by firstly providing a double "drawing" punch cut and subsequently providing a double drawing shearing cut. The cutter punches the work with a point to produce a hole and is then swung in an arc to complete the shearing cut.
Other apparatuses pertinent to the problem of cutting metal shapes include that of Henry C. Jones U.S. Pat. No. 535,207, wherein knives cut through the web of a beam and subsequently sequentially cut the flanges.
In U.S. Pat. No. 786,236 of William Ross, a press is shown having a pair of blades in cooperating stationary shearing devices.
In Hugo John U.S. Pat. No. 841,979, a metal cutting machine is disclosed wherein an upper cutter is mounted on a balance beam rotatable about a pin to cut the iron by movement in opposite directions.
In U.S. Pat. No. 861,122 of Hugo John, a metal cutting machine is shown providing both left cuts and right cuts of the girder flanges.
In U.S. Pat. No. 995,252 of Hugo John, a girder cutting device is shown wherein T girders are cut in a downward operation and a subsequent upward operation with the girder being moved laterally prior to making the second cut.
E. V. Wurtz discloses, in U.S. Pat. No. 1,241,259, a machine for operating on structural beams wherein cuts on the flange and web are made in successive operations. The cutter has a plurality of cutting edges for cutting different portions of the beam.
Thomas D. Williams, in U.S. Pat. No. 1,758,019, provides shearing blades which firstly cut downwardly to penetrate the material to be sheared and which are then forced apart to shear the material on opposite sides of a penetrating point. The blades are spread outwardly in opposite directions to effect simultaneous cutting by each of the blades.
A. S. Liss et al, in U.S. Pat. No. 2,413,980, show a shearing apparatus utilizing a cam member for moving a shearing die for cutting different portions of the workpiece.
Kurt W. Nebel, in U.S. Pat. No. 2,581,694, discloses shears which initially pierce the work to permit a subsequent free swinging of the cutting unit to complete the shearing of sheet metal.
Charles M. Brehm, in U.S. Pat. No. 2,837,156, shows a tube cutting die having shearing strokes substantially perpendicular to each other in cutting tubular stock.
Joseph W. Reis et al, in U.S. Pat. No. 3,451,297, show a shearing device utilizing a primary die and a secondary die for minimizing die stresses and preventing formation of an edge burr on the sheared material.
In one prior art tube cutoff device, a pointed blade is moved vertically into the tube and a horizontal blade is provided for cutting horizontally to provide a two-step cutting operation.